I agree. This is snake oil.
Once you learn a bit about water chemistry, you understand which additions raise your pH, and which lower it. But my additions would be different than your additions - even if we have the same goals - because my water almost certainly has different concentrations of the various ions important to brewing (i.e. calcium, sodium, magnesium, chloride, etc), different starting pH, etc.
So tell me this - how can one "off the shelf" product magically give ideal finishing water, when it cannot possibly take into account the wide variety of water that brewers use? The answer, quite simply, is that it cannot.